The National Health and Nutrition Examination Survey is an on-going, national, comprehensive health survey of the civilian, non-institutionalized US population. A vision assessment was added in 1999 and is on-going; revisions to the protocol were made this year and will be effective for the 2003 data collection cycle. All sample persons aged 12+ years undergo a vision assessment in which measures of the eyeglass prescription in people who wear glasses for distance, tests the distance visual acuity of sample persons with and without correction (glasses/contacts) and an objective refraction (incorporating also an evaluation of the corneal curvature of the eye) are obtained. A visual acuity at near is assessed in persons age 50 years and over. In addition, personal interview data on functional measures related to vision are collected on people over the age of 49 years. Data from the vision component in NHANES will be used to estimate the prevalence of visual impairment in the U.S. population, describe the distribution of refractive error in the U.S. population, evaluate the impact of vision loss on functional abilities, and relate visual impairment to other health and disease measures. The prevalence data will be used as baseline measures for Healthy People 2010.